The quantitative determination of analytes in body fluids is of great importance in the diagnoses and maintenance of certain physiological abnormalities. For example, lactate, cholesterol and bilirubin should be monitored in certain individuals. In particular, it is important that diabetic individuals frequently check the glucose level in their body fluids to regulate the glucose intake in their diets. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered.
In some existing techniques, a lancet may be used to draw fluid (e.g., blood) from a user. This fluid is then used with an instrument or meter to determine an analyte concentration. It would be desirable to eliminate the need to use a lancet, while still accurately determining the analyte concentration. Such applications are referred to as non-invasive techniques.
One non-invasive technique involves using Raman signals to determine the concentration of an analyte such as glucose. There, however, are disadvantages in existing non-invasive methods that use Raman or other types of signals. For example, the spectral image of an object that is imaged using a spectrometer contains optical aberrations. Optical aberrations such as curvature may result in overlapping spectral bands and/or poorly resolved peaks. This may lead to erroneous results when attempting to quantify an analyte in a complex matrix. These optical aberrations may make it difficult to distinguish or differentiate analytes (e.g., glucose) from other tissue and fluid components with similar characteristic spectra. Some existing techniques have proposed hardware solutions to correct the optical aberrations. These hardware solutions, however, do not have the flexibility to address selected optical aberrations. For example, existing hardware techniques are not adapted to address curvatures that are not fixed such as those associated with holographic or transmission grating.
It would be desirable to have a method that has flexibility in addressing a variety of optical aberrations in spectral images.